(1) Field of the Invention
This invention relates to a semiconductor device and a method for fabricating such a semiconductor device and, more particularly, to a semiconductor device with a heat sink mechanism and a method for fabricating such a semiconductor device.
(2) Description of the Related Art
The semiconductor integrated circuit element which is a kind of semiconductor device includes electronic circuits formed by interconnecting active elements, such as transistors, and passive elements, such as capacitive elements, formed on a semiconductor substrate made of silicon or gallium arsenide.
To stabilize the operation of electronic circuits, a semiconductor integrated circuit element (semiconductor element) is sealed by an insulator, such as resin, or is put into a container hermetically sealed.
With such a semiconductor device, it is necessary to radiate heat which is generated in a semiconductor element at the time of the operation of electronic circuits to the outside.
For example, a heat sink structure shown in FIG. 40 has traditionally been used for radiating heat.
FIG. 40 shows a semiconductor device 400 of what is called a ball grid array (BGA) type.
FIG. 40A shows the top of the semiconductor device 400 and FIG. 40B shows a section along lines X-X of FIG. 40A.
With the semiconductor device 400, a semiconductor element 403 is mounted over a wiring board 401 with an adhesive material 402 therebetween. Electrodes of the semiconductor element 403 are connected to terminals 401a located over the wiring board 401 by bonding wires 404.
In addition, a heat sink member (heat spreader) 406 stuck over the wiring board 401 by an adhesive material 405 is located over the semiconductor element 403 so as to cover the semiconductor element 403.
A sealing resin 407 is located between the heat sink member 406 and the semiconductor element 403 and an outer side of the heat sink member 406 is covered with the sealing resin 407.
On the other hand, a plurality of solder balls are located on or under an other surface of the wiring board 401, that is to say, on or under a surface of the wiring board 401 opposite to the surface over which the semiconductor element 403 is mounted as external connection terminals 408.
With the semiconductor device 400 having the above structure, heat generated in the semiconductor element 403 is transmitted to the heat sink member 406 mainly via the sealing resin 407 which covers the semiconductor element 403, and is released from a top 406a of the heat sink member 406 to the outside.
In addition to the above semiconductor device, a semiconductor device of the BGA type (see Japanese Patent Laid-Open Publication No. 2000-294694) in which a first heat sink member is located on the side of a top of a semiconductor element mounted over a wiring board and in which a second heat sink member which pierces the wiring board is located on the side of the reverse of the semiconductor element or a semiconductor device (see Japanese Patent Laid-Open Publication No. 2005-109526) in which a semiconductor element located between a pair of flat-plate heat sink members with solder or the like therebetween is sealed by resin is proposed as a semiconductor device with a heat sink mechanism.
With the above-mentioned semiconductor device of what is called the BGA type, most of the surface of the wiring board 401 where the semiconductor element 403 is mounted is covered with the sealing resin 407 in order to physically and chemically protect the semiconductor element 403 and the heat sink member 406 which covers the semiconductor element 403.
However, the thermal conductivity of the sealing resin 407 is comparatively low. This contributes to a decrease in the efficiency of heat sink of heat generated in the semiconductor element 403 to the outside via the heat sink member 406.